Fix Symbol#sourceFile

defTree should take precedence over associated files. This matters for
inlined code.

Author: odersky

compiler/src/dotty/tools/dotc/core/Symbols.scala

@@ -624,21 +624,22 @@ object Symbols {
     type DontUseSymbolOnSymbol
 
     /** The source file from which this class was generated, null if not applicable. */
-    final def sourceFile(implicit ctx: Context): AbstractFile = {
-      val file = associatedFile
-      if (file != null && file.extension != "class") file
-      else if (!defTree.isEmpty) defTree.source.file
+    final def sourceFile(implicit ctx: Context): AbstractFile =
+      if (!defTree.isEmpty) defTree.source.file
       else {
-        val topLevelCls = denot.topLevelClass(ctx.withPhaseNoLater(ctx.flattenPhase))
-        topLevelCls.unforcedAnnotation(defn.SourceFileAnnot) match {
-          case Some(sourceAnnot) => sourceAnnot.argumentConstant(0) match {
-            case Some(Constant(path: String)) => AbstractFile.getFile(path)
+        val file = associatedFile
+        if (file != null && file.extension != "class") file
+        else {
+          val topLevelCls = denot.topLevelClass(ctx.withPhaseNoLater(ctx.flattenPhase))
+          topLevelCls.unforcedAnnotation(defn.SourceFileAnnot) match {
+            case Some(sourceAnnot) => sourceAnnot.argumentConstant(0) match {
+              case Some(Constant(path: String)) => AbstractFile.getFile(path)
+              case none => null
+            }
             case none => null
           }
-          case none => null
         }
       }
-    }
 
     def source(implicit ctx: Context): SourceFile = ctx.getSource(sourceFile)